States rights on motor vehicle regulations. But in general it seems the most common requirements are to show the DMV official that it has a permanent toilet, bedroom, and kitchen.
I was surprised here in Washington State. Went down to the state patrol office to make an appointment to have my mini conversion inspected and they said write out a statement that it has been converted to a motor home and sign it. That was it. New title arrived in a few weeks.
This google search found some info kentucky bus conversion titlehttp://www.skoolie.net/forums/f6/hello-from-southern-kentucky-16730.htmlOnly looked at this but it seems KY DMV does not deal with this very well; that is, getting motorhome title on a converted bus. But one guy did get insurance as a bus, some failed. The other thing is if it is titled as a bus it will be governed by commercial vehicle laws meaning you'd need a CDL to drive it. anyway good luck, plenty of resources out there.
It's also possible to get transit tags in most states, which would allow one to drive a seated bus home without registering it. I believe that many carriers will also issue transit liability coverage, but that might be more difficult.Of course, if the bus is still seated, you'll need a CDL.